1. Field of the Invention
The present invention relates to a technology of manufacturing an optical waveguide apparatus using an SOI substrate having a silicon thin film on a quartz substrate.
2. Description of the Related Art
With recent spread of the Internet, a high-speed and high-capacity optical communication system has been considerably developed. At the present day, FTTH (Fiber To The Home) which is an optical communication network configuration scheme that directly leads an optical communication cable to a personal residence of a general user has become widely used, and a study for enabling a light in a band of 1.55 μm as typified by a C band or an L band to be propagated through an optical waveguide provided on an optical integrated circuit has been advanced.
Among others, a study on a single-crystal silicon waveguide using an SOI substrate has been actively conducted (see, e.g., Japanese Patent Application Laid-open No. 2006-195371, Japanese Patent Application Laid-open No. 2005-157210, Japanese Patent Application Laid-open No. 2004-086868, Japanese Patent Application Laid-open No. 2002-323633 and others) because the SOI substrate is a substrate previously including a high-quality single-crystal silicon layer suitable for suppressing a propagation loss at minimum and a silicon oxide film that can be used as a clad layer of an optical waveguide.
However, in view of an optical communication system, a general-purpose platform of an optical integrated circuit on a practical level is not present under the present situation even though a fusion technology of not only a technology of using an SOI substrate to form a single-crystal silicon waveguide but also a modulation mechanism for modulating an optical signal or any other device (e.g., a receiving optics or an optical fiber) is important, and conventionally proposed technologies are all on a study stage. In particular, a technology of monolithically integrating a mechanism for modulating a light in a band of 1.55 μm with a light having a short wavelength (a wavelength: approximately 0.85 μm) as typified by GaAs is yet to be completed.
In view of such a problem, it is an object of the present invention to provide an optical waveguide apparatus having a very simple structure that can modulate a signal light guided through an optical waveguide and, more particularly an optical waveguide apparatus in which a mechanism that can modulate a light in a band of 1.55 μm with a light having a short wavelength as typified by GaAs is monolithically integrated.